Dynamo-electric machine.



C. L. KENNEDY.

DYNAMO ELECTRIC MACHINE.

APPLICATION FILED APR. 5. 1916.

1,238,923. Patented Sept. 4,1917.

DC. DC.

Invewlorw the successive poles which the generator-' nately by oppositely-extending UNITED STATES PATENT OFFICE.

CARLTON L. KENNEDY, CF SOUTH BRAINTREE, MASSACHUSETTS, ASSIGNOB TO THE HOLTzEB-CABOT ELECTRIC COMPANY, OF BOXBURY, MASSACHUSETTS, A CORPO- vDrumso-nmao'rnro MACHINE.

To may concern: a

Be it known that I, CARLTON L. KENNEDY,

a citizen of the United States, residing at South Braintree, in the county of Norfolk and State of Massachusetts, have invented certain new and useful Improvements inchines of the dynamotor type, in'which analternating current is induce in a generatorwinding laced upon the core of an armature, w e the armature is rovided with an independent winding, whic may be used as either a motor-winding or a generatorwinding. In certain machines of that type which have been heretofore proposed each cycle of the generated current results, not

from two reversals of the magnetic flux cut by any one conductor of the generator-winding, as in the ordinary dynamotor or alternating-current generator, but rather to the two fluctuations, without reversal of polarity, which occur in the field cut by each conductor as it passes and then recedes from a single polar projection of the field-magnet.

For the foregoing purpose each field-pole is made to occupy approximately the same angular space as one, or any odd number, of

winding is arranged to produce in the armature. In this arrangement the part of the.-

field which is of greatest intensity at any given polar projection is traversed altergeneratorconductors, so that an alternating current is set up 'of a fre uency e ual to one-half the number of con uctors ior groups of conductors of like direction) which passes any one polar projection in a unit time. If the armature 1s of the slotted type, as is generally preferable, with each tooth constituting a pole of the generator-winding, the two teeth which are at the same moment respectively approaching and receding from each i Specification of Letters Patent.

field-pole undergo changes of flux in oppos1te senses, and these changes of flux pro- Patented Sept. 4, 1917.

Application filed April 5, 1916. Serial No. 89,120.

duce, in the corresponding oppositely arranged co1ls, electromotive forces which are effective in the same direction in-the A. C. generator-winding as a whole:

In order that the field ole's of opposite si may have additive e ects on the A. C. winding, they are so arranged that the space between adjacent poles of opposite sign is approximately equal to that of an even number of the poles which the generator-windin is'arranged to produce in the armature.

' ith the foregoing relations of the arts, the number of cycles of the generate current for each rotation of the armature does not depend, as in the ordinary dynamotor, upon the number of field-poles, but is determined solely b the number of poles produced by the A. winding.

The mode of operation above described is independent of the number of field-poles and polar projections, but to secure the highest efficiency it is necessary to have as man as possible of the conductors of the A. G. wmdmg operative at the same time, and to this end it has been proposed to divide each pole of the field-magnet among a plurality of polar projections, and space these projections so that they shall act simultaneously, in the same sense, upon a series of armature coils. For this'purpose the polar projections of each pole must be located with their center-lines spaced by an angular distance corresponding to that of an even number of armature-poles, and preferably by the space of two armature-poles only. The number of such projections isyariable, and it depends largely upon the size of the machine and the number of field-poles, while being entirely independent of the frequency required.

The present invention relates to dynamoelectric machines of the type just described, and the object of the invention is to produce a machine having a relation of the poles of the field-magnet and the armature, and an arrangement of the armature-windings, which will tend to minimize the inductive action of the A. C. winding onthe D. C. winding, and also will insure the presence of commutatin zones of such width as to suppress sparking, regardless of the size of the machine and the number of poles.

To the foregoing ends it is proposed, in

accordance with the present invention, to so arrange the polar projections of the fieldmagnet that the nearest projections of two field-poles of opposite sign are spaced with their center-lines at an angular distance equal to that of an odd number not less than three of the poles of the A. C. armaturewinding, while the D. C. armature-winding is arranged to have an even pitch. The said arrangement of the field-projections slightly reduces the theoretical cfiiciency of the machine, in so far as it leaves certain parts of the A. C. winding idle at the commutation zones, but this arrangement, in combination with the use of a D. O. winding of even pitch, affords a neutral commutation zone includ ing an integral plurality of poles of the D. C. winding, from which it results that good commutation is secured regardless of the multiplication of the poles of the A. C. wind- The use of a D. C. armature of even pitch, in addition to contributing to good commutation as just set forth, has the further advantage that the two opposite parts of each coil of the D. C. winding lie beside stretches of the A. C. winding in which the current is.

flowing in opposite senses, relatively to the said coil, so that the inductive efi'ect of the alternating current on the D. C. coils is. entirely balanced and causes no flow through the coil.

The accompanying drawing is a diagrammatic representation of a dynamo-electric machine embodying the present invention.

The invention is illustrated as embodied in a machine in which the armature has a core 1 with 28 slots. On this core is a direct-current winding 2, into and out of which the current is led through the usual commutator 3, by brushes 4 connected with current-leads 5. The details of the winding 2 are not shown, except that it is indicated, by dotted lines 6, that each coil spans an even number of teeth.

The core 1 is also provided with an A. C.

generator-winding 7. arranged in the sameslots as the motorwviruling. The winding 7 may be either a zig-zag winding or a winding comprising one or more turns arranged reversely on adjacent teeth. The terminals 8 of the A. C. generator-wimling are connected to collector-rings 9, from whichthe alternating current is taken off by brushes 10.

The field-magnet 11 is of the %-pole type, and at each pole there are three polar projections 12. The field-winding is in the form of coils 53, each of which surrounds the three projections at one of the poles of the magnet. These coils are connected, in series, across the current-leads 5.

The polar projections 12 of each group are spaced apart an angular distance equal to that of two teeth or slots of the arnnu ture, so that as the teeth move past the projec'tions every alternate tooth is moving from a o'int of greater magnetic intensity to a point of lesser magnetic intensity, while the intermediate teeth are moving from points of lesser intensity to points of greater intensity. The nearest polar projections of opposite sign, on the other hand, are spaced with their center-lines at a distance corresponding to three teeth or three slots.

It will be apparent that with the arrange ment of polar-projections and teeth illusand accordingly the number oi field-poles. may be selected with regard primarily to.

convenience in construction and the eflicieney of the machine as a motor, while any multiplication of slots in the armature, tor the purpose of securing high trequenc is rather conducive than detrimental toe icient motor-operation.

When the illustrated machine is used as a dynamotor' direct current is supplied, through the leads 5, to the D. C. armaturewinding and the field-winding, and the armature then rotates like that of a motor, while alternating-current is generated in the Winding 7. The machine may, however, be used as a seltt-exciting generator. In this case power is applied to rotate the armature, and the direct current generated in the armature-winding 2 is utilized to energize the field-magnet, while the alternating current generated in, the winding 7 constitutes the useful result of the operation.

In. the illustrated arrangement of the A. C. winding each coil embraces a single tooth ot the armature, so that the poles of the A. (3. winding correspond in number and in location. with. the teeth. It will be apparent, however, that. the invention is equally applicable toother arrangements such, for example, as asmooth armature in which there are no. teeth, or a distributed or overlapping arrangement of the A. G. winding in. which a plurality of. aijmature-tecth are embraced in or correspondto each pole of the winding.

I claim: 1. A. dynamo-electric machine having, in combination, an armature-core; an alternating-current winding thereon arranged for I alternate poles; a direct-current winding of: even pitch; and a multipolar field-magnet of which each pole is provided with a plurality of polar projections which are spaced. Withtheir center-lines at, anangular distance equal to that of an even number of armature poles.

2. A dynamo-electric machine having, in combination, an armature-core; an alternating-current winding and a direct-current winding thereon, the former being arranged for alternate poles and the latter being of even pitch; and a multipolar field-magnet of which each pole is provided with a plurality of polar projections, which are spaced with their center-lines at an angular distance equal to that of an even number of armaturepoles, while the nearest polar projections of two field-poles of opposlte sign are spaced with their center-lines at an angular distance equal to that of'an odd number, not less than three, of the armature-poles.

3. A dynamo-electric machine having, in combination, an armature comprising a slotted core, a direct-current winding thereon of even pitch, and an alternating-current winding arranged for like polarity of alternate core-teeth; and a multipolar field-magnet of which each pole is provided with a plurality of polar projections which are spaced with their center-lines at an angular distance equal to that of an even number of armature-teeth.

CARLTON L. KENNEDY. 

